National insurance claim settlement money

My car zen was stolen in june 2009.It was fitted with cng which was also insured. Upon the settlement of claim only th eamount minus cost of cng unit was recd by me on the pretext that the policy was not updated in their system for the cng whereas the same was paid by me and the policy covernote was produced. Toill date I have been running pillar and post without any result.Kindly help. Thanks & regards